The present invention relates to a rigid structure made of composite-material for a vehicle seat element, and to methods of making such structures.
More particularly, amongst such structures, the invention relates to those formed as a single piece made from a composite material comprising a thermoplastic matrix and reinforcing fibers, the structure comprising at least firstly first and second rigid sideplates each extending between a first end and a second end, and secondly a rigid horizontal cross-member secured to the second ends of the sideplates.
Such structures for seat elements formed by vehicle seat backs are described in particular in U.S. Pat. No. 6,059,369. Those seat back structures may be provided with a central core of foam having braids molded around them, the braids comprising glass fibers and/or carbon fibers impregnated in thermoplastic resin. When preparing the central core of foam, small diameter metal bushings may be integrated in the core for the purpose subsequently of receiving pivot mechanisms for pivotally connecting the rigid seat back structure to a rigid structure for the seat proper of the vehicle seat.
Thus, in order to be able to fix a pivot mechanism on the metal bushing integrated in the central foam core covered by composite fiber braids, it is necessary to perform an additional step during final assembly of the seat, thereby increasing the time required to assemble said seat, and thus its manufacturing cost.
Furthermore, the small size of the metal bushing that is to receive the hinge provides little contact area between the composite reinforcing fibers and the metal bushing, which can lead to the connection between the bushing and the composite fibers breaking when the hinge is subjected to large forces.
An object of the present invention is to solve the technical problems posed by the above-mentioned state of the art.
According to the present invention, this object is achieved by the facts that the structure further comprises at least one hinge having a first fixing portion secured to the structure, a second fixing portion for fixing to another seat element, and a hinge mechanism interconnecting the first and second fixing portions and actuatable by a control member so that said first and second fixing portions are either free to pivot relative to each other about a pivot axis or else are locked angularly relative to each other, and that the first fixing portion of the hinge is overmolded by the first end of the first sideplate.
In preferred embodiments of the invention, recourse is also made to one or more of the following dispositions:
a portion of the first end of the first sideplate in contact with the first fixing portion of the hinge presents a housing having an end wall pressed against the first fixing portion of the hinge, and a side wall extending from said end wall and covering the first fixing portion of the hinge axially, at least in part;
the side wall of the housing of the first end of the first sideplate presents a curved edge which extends radially towards the pivot axis of the hinge;
the first fixing portion of the hinge comprises a plurality of elements in relief onto which the first end of the first sideplate is overmolded;
the composite material comprises a tubular braid of reinforcing fibers including a segment forming the first end of the first sideplate which presents a section that is substantially flat and double-walled;
the first end of the second sideplate includes a pivot element for pivotally mounting on the other seat element, said pivot element being integrally formed with the first end of the second sideplate;
a second hinge is also overmolded by the first end of the second sideplate of the structure;
the structure also comprises a second rigid horizontal cross-member having a first end integrally formed with the first end of the second sideplate and a second end overmolded on the first end of the first sideplate; and
the structure is formed by a rigid structure for a seat back.
The invention also provides a method of manufacturing a rigid structure for a vehicle seat element, said structure comprising firstly first and second rigid sideplates each extending between a first end and a second end, and secondly a rigid horizontal cross-member secured to the second ends of the sideplates, said cross-member and the sideplates being made as a single piece out of a composite material comprising a thermoplastic matrix and reinforcing fibers, the method comprising the following steps:
providing a hinge comprising a first fixing portion, a second fixing portion for fixing to another seat element, and a hinge mechanism interconnecting the first and second fixing portions and actuatable by a control member so that the first and second fixing portions are either free to pivot relative to each other about a pivot axis or else are angularly locked relative to each other; and
the composite material portion forming the first end of the first sideplate is overmolded onto the first fixing portion of the hinge.
In preferred implementations of the invention, recourse is also made to one or more of the following dispositions of the method:
the composite material comprises a tubular braid of reinforcing fibers, said method comprising the following steps:
inserting an inflatable bladder in the tubular braid;
placing the hinge in a mold defining a cavity of shape complementary to the outside shape of the structure;
placing the tubular braid in the mold; and
heating the mold and inflating the inflatable bladder under pressure to compress the tubular braid against the cavity of the mold and to cause the thermoplastic matrix to melt which matrix, after hardening, enables said structure to be obtained, the braid portion forming the first end of the first sideplate being compressed and overmolded onto the first fixing portion of the hinge;
prior to the tubular braid hardening, the hinge is moved towards the first end of the first sideplate along the pivot axis to bond together at least two portions of the first end of the tubular braid placed facing each other;
prior to placing the tubular braid in the mold, a second hinge is placed in the mold, and while the inflatable bladder is being inflated, the portion of the tubular braid that forms the second end of the second sideplate is pressed against and overmolded onto the second hinge;
the tubular braid is of a length that is suitable for forming a second horizontal cross-member having a first end formed integrally with the first end of the second sideplate, and a second end which, during inflation of the inflatable bladder, is compressed and overmolded onto the first end of the first sideplate against which the hinge is overmolded; and
the mold is provided with at least two projecting members to enable two diametrically opposite portions of the tubular braid to be compressed during inflation of the inflatable bladder respectively against the associated projecting member, thereby forming two blind holes each having an inside wall, each blind hole subsequently being pierced, once the thermoplastic matrix has hardened, so as to form a through housing with an inside wall in the structure of the seat element.